JPS625321B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a non-linear resistor, and in particular to a method for manufacturing a non-linear resistor, which improves the mixing of zinc oxide and metal oxide and reduces variations in the electrical characteristics of the non-linear resistor. The present invention relates to a method for manufacturing a linear resistor.

In electrical systems, overvoltage protection devices are used to remove overvoltages superimposed on normal voltages and protect the electrical systems.

This overvoltage protection device uses a non-linear resistor that exhibits almost insulating properties at normal voltage and has a relatively low resistance value when overvoltage is applied.

Non-linear resistors are made by mixing silicon carbide (SiC) or zinc oxide (ZnO) with metal oxides and firing the molded material.

For example, ZnO 76 mol%, magnesium oxide (MgO) 16 mol%, bismuth oxide (Bi ₂ O ₃ ), antimony oxide (Sb ₂ O ₃ ), cobalt oxide (CoO), manganese oxide (MnO), chromium oxide (Cr ₂ O) ₃ ) and 0.05 to 3.5 mol% of iron oxide (Fe ₂ O ₃ ) each in a total of 8
mole %, weigh and mix.

Press and mold the mixture at 1200℃ to 1300℃
Baked for 8 hours at a temperature of ℃, diameter 60mm, thickness 10mm
A material for a disc-shaped nonlinear resistor is made, and electrodes are formed using a metal spraying method to form a nonlinear resistor.

Non-linear resistors manufactured in this way have the disadvantage that in the process of mixing multiple types of metal oxides, it is difficult to mix them homogeneously, resulting in variations in the electrical characteristics of the manufactured non-linear resistors. There was a need for a manufacturing method that would yield a homogeneous mixture.

The present invention has been made in view of the above-mentioned needs, and provides a method for manufacturing a non-linear resistor that can reduce variations in the electrical characteristics of the manufactured non-linear resistor.

Next, embodiments of the present invention will be described.

For example, 80 mol% ZnO and at least one metal oxide, such as 14 mol% MgO, 2 mol% Bi ₂ O ₃ , 1.5 mol % Sb ₂ O ₃ , 1.1 mol % CoO, 0.5 mol % Cr ₂ O ₃
Weigh in the proportions of mol%, MnO 0.5 mol%, Fe ₂ O ₃ 0.4 mol%.

Next, the weighed oxide is crushed with water, and
Mix oxides.

When solids such as metal oxides are mixed with water and ground, the water and solids separate within a short time after grinding, and oxides with high specific gravity and oxides with low specific gravity can be separated. Stabilizers are added to prevent this from separating.

The stabilizer is preferably sodium alginate, ammonium alginate, or hydroxypropylcellulose, and the mixing ratio is preferably 1/1000 to 20/1000 of solids by weight.

The oxide, water, and mixed stabilizer are placed in an attritor, and the attritor is operated for about 3 hours to crush the oxide and mix the water and mixed stabilizer.

The oxide is then placed in a dry granulation device, such as a spray dryer, to form spherical agglomerates having a particle size of, for example, 100 to 300 microns.

This powdered mixture is pressed through a press, e.g.
Form into a disc of 100mm and 25mm thick.

This molded product is placed in an electric furnace and fired. The firing temperature is approximately 1300°C, and the appropriate time is, for example, 6 hours.

After firing, the disc-shaped fired product shrinks more than before firing, but has a substantially homogeneous composition and density.

Next, both sides of the disc-shaped fired product are lightly polished to expose the fired product. For example, aluminum is metal sprayed on this exposed surface to form electrodes and the nonlinear resistor is completed.

The degree of variation in the nonlinear resistors manufactured in this manner is shown in FIGS. 1 and 2.

FIG. 1 shows the variation in firing voltage when a non-linear resistor designed with a firing voltage of 4000V was manufactured using different stabilizers. The horizontal axis shows the discharge starting voltage, and the vertical axis shows the number of occurrences when the manufacturing quantity is set to 100% as a relative value. Curve A shows sodium alginate as a mixed stabilizer in a weight ratio to the weight of solids.
Shows the case of mixing 10/1000. Curve B shows 1000% of ammonium alginate as a mixed stabilizer.
10.Curve C is hydroxypropylcellulose
This is the case when 10/1000 of each are mixed. Curve D shows an example of a non-linear resistor produced by a conventional manufacturing method.

As described above, it was confirmed that the nonlinear resistors produced by the manufacturing method of the present invention were concentrated near the designed discharge starting voltage of 4000 V, and the variation in electrical characteristics was small.

FIG. 2 shows the rate of change in discharge starting voltage when the mixing amount of sodium alginate was changed. 10 to 40 samples were made with varying amounts of sodium alginate mixed, the discharge voltage was measured, and the variation in discharge voltage for the same amount of mixture was calculated. When the amount of stabilizer mixed is 1/1000 to 20/1000 of the solid content in weight ratio, the voltage fluctuation is about 5%, but even if the amount of stabilizer is less than 1/1000, Further, even if the amount was more than 20/1000, the dispersion of the discharge starting voltage would increase, making it unsuitable for use as a nonlinear resistor.

Even when non-linear resistors were manufactured by changing the mixed amounts of ammonium alginate and hydroxypropyl cellulose, a similar tendency was observed, and the amount of mixed stabilizer was in the range of 1/1000 to 20/1000 of the solid content. The inside was preferable.

As described above, according to the present invention, zinc oxide and at least one metal oxide are mixed together with water and a mixed stabilizer, and sodium alginate, ammonium alginate, or hydroxypropylcellulose is used as the mixed stabilizer, and the metal oxide is The mixing ratio to solid content is 1/1000 to 1/1000 by weight
By adding 20/1000 and mixing, a nonlinear resistor with less variation in electrical characteristics can be manufactured.

[Brief explanation of the drawing]

FIGS. 1 and 2 are curve diagrams illustrating the electrical characteristics of nonlinear resistors manufactured using the manufacturing process of the present invention, respectively.

Claims (1)

[Claims] 1. A step of mixing zinc oxide and at least one metal oxide with water and a mixed stabilizer, a step of drying the mixture, and a step of firing the dried product,
forming an electrode on the fired product, using sodium alginate, ammonium alginate, or hydroxypropyl cellulose as the mixing stabilizer, and setting the mixing ratio of the metal oxide to the solid component to be 1/1000 to 1/1000 by weight. A method for manufacturing a non-linear resistor, characterized in that the resistance is 20/1000.